Data flow: Add stub expectsContent for all languages

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -800,6 +800,12 @@ predicate clearsContent(Node n, ContentSet c) {
   FlowSummaryImpl::Private::Steps::summaryClearsContent(n, c)
 }
 
+/**
+ * Holds if the value that is being tracked is expected to be stored inside content `c`
+ * at node `n`.
+ */
+predicate expectsContent(Node n, ContentSet c) { none() }
+
 private newtype TDataFlowType =
   TTodoDataFlowType() or
   TTodoDataFlowType2() // Add a dummy value to prevent bad functionality-induced joins arising from a type of size 1.